Loose leaf binders and similar devices are well known in the prior art. Exemplary of prior devices are those disclosed in U.S. Pat. Nos. 3,612,709; 4,056,326; and 4,761,091 which relate to the means by which replaceable leaves of paper are loosely held or bound within binders generally having front and rear covers. Common types of such binders are the extensible-post binder, such as described in U.S. Pat. No. 4,056,326, and the commonly available "three-ring" binder.
A prior file folder or paper binder device for which this invention is designed normally includes a front cover and a rear cover which are hingedly connected to a backbone portion so that the covers swing on definite hinge lines at the edges of the backbone, which is generally of fixed width. Means for retaining paper within the binder device is also normally included arranged on or adjacent the backbone portion of the binder. Such retaining means includes the well-known three-ring binding mechanism as well as the extensible-post binding mechanism.
Binders of the aforementioned type are becoming more and more useful in education and business to bind loose papers, catalogs and the like. Unfortunately, however, the storing of such binders is particularly awkward. Specifically, while the the inner edges of the covers adjacent the backbone portion of the binder are generally a fixed distance apart because of the fixed width of the backbone portion, the spacing between the outer edges of the cover is a function of the quantity of paper in the binder. When the binder is less than substantially full, the outer edges of the covers converge toward one another so that they are closer to one another than the inner edges of the covers. In fact, if only a few or no papers are in the binder, the outer edges of the covers may actually touch each other. The converging arrangement of the covers when observed in a plan view from above resembles a wedge or pie slice.
It is difficult to maintain these prior binders in a neat, orderly arrangement upon a shelf or between bookends because of the asymmetry caused by the nonparallel arrangement of the front and rear covers of the binders. As noted, binders of the aforementioned type are becoming more and more useful to society, and there has developed a particular need for the ability to stack or shelve such binders in a neat and orderly fashion.